Among vehicle body frame structures of the above-mentioned type, heretofore, there has been a vehicle body frame structure including a frame structure body which has a suspension supporting section (right and left cushion top end supporting parts, right and left upper arm supporting parts, and right and left lower arm supporting parts) for supporting the respective right and left wheels. The frame structure body is configured chiefly of multiple cast parts (frame components) (see Japanese Patent Application Laid-open Publication No. Hei. 08-197967, for example). In this vehicle body frame structure, the frame structure body is composed of two mutually-independent, virtually identical parts—a right and a left cast parts, which are then welded together.